This invention relates to HF radar.
It particularly relates to RF radar installations consisting of arrays of receive/transmit modules and to modules for use in such installations.
As depicted in FIG. 1, whereas microwave radar is generally limited to line-of-sight surveillance. HF radar allows xe2x80x9cover-the-horizonxe2x80x9d surveillance to be made.
It is the practice in HF radar to provide different antennas for transmission and reception. FIGS. 2 and 3 depict an example of a prior art HF radar consisting of a transmitting antenna 20, receiving, antenna 30, RX/OPS cabin 32, TX/OPS cabin 22 and generator 34.
In order to provide the necessary directivity and radiation efficiency, the prior art HF radar utilises a transmitter antenna consisting of a conventional phased array. To obtain a satisfactory efficiency, the prior art has utilised relatively tall antennas so that the radiating elements are as high as possible. This has required the use of substantial bracing and/or substantial concrete foundations for each antenna element. To avoid excessive leakage of transmitted signal into the front end of the receiver, a discrete receiver antenna 30 is provided some distance from the transmit antenna array. The individual antenna elements of each array have also had to be disposed in accurate spatial relationship with each other. While this prior art arrangement has been found to be satisfactory in terms of its effectiveness as a radar, it does require the availability of a level site of substantial area and linear extent and the accurate spacing of the individual elements of the transmit antenna in particular. While such an arrangement may well be satisfactory for a permanent installation, it is not easily implementable as a mobile or temporary transportable installation which can be set up quickly on an unprepared site, or on poor, relatively weak, ground such as marshland or beaches. The present invention seeks to provide an arrangement in which the disadvantages of the prior art are at least ameliorated.
A first aspect of the invention provides a transmit/receive assembly for a HI radar apparatus, the transmit/receive assembly comprising a power transmitter for generating radio frequency signals, a receiver for receiving radio frequency signals and a duplexer arranged to couple the output of the power transmitter and the input of the radio receiver to a common port connection to a transmit/receive antenna.
A second aspect of the invention provides a transmit/receive antenna assembly comprising a transmit/receive assembly in accordance with the first aspect of the invention and an antenna.
A third aspect of the invention provides a HF radar comprising such transmit/receive assemblies or transmit/receive antenna assemblies.